2002 passat tdi cold start problem.

On cold mornings wont start.turns over for twenty seconds then fires up new glow plugs put in new battery, temp sensor as well.glow plugs not coming on so changed relay as well,running out of things to change please help.

I had the same problem - would not start cold; but I unplugged the temp sensor, and found I had 12 volts at the end of the wiring harness. Did you unplug the temp sensor before checking the output of the harness?

My problem ended up being air leaking into the fuel filter from the fuel return line.

unplugged temp sensor and plugs came on,but still the same problem.I shall cheek the fuel line.

You can just look at the clear fuel line. If you see bubbles, then there may be a problem.

It seems the VW canister fuel filter sometimes has a faulty connection (plug) from the fuel return line. If you press on the plug, then bubbles start and stop.

That's how I found mine. Also, make sure the hose clamps are tight.

cheers,but my problem only in the morning,would the air leak not cause problem all day long

In my situation, I would try to start my 03 Golf TDI in the morning; and it would just crank and crank and crank. Then after about 30 seconds or so, it would finally, but reluctantly start, hardly run; but then run fine after a while.

So after that, it would run fine; and it would also start again easily after it warmed up.

At first, I though it was the glow plugs; so I checked them with the ohm meter. GPs were okay.

Then I checked the glow plug harness, the GP fuse, tested the relay, etc. etc.

I almost gave up, but then after finally getting it started, I was staring under the hood and thinking what could be wrong - all this while the car was running.

Then I saw a tiny stream of bubbles in the incoming fuel line.

After I tightened all the fuel connections, it started right up the next cold morning. My problem got solved.

But to answer your question: Yes, the air leak was happening all day. The TDI can take an air leak, but only after it runs a while.

Apparently, the fuel injector pump needs to for full for a fast start.

Great i shall that tomorrow fingers crossed,keep an eye on this thread for
result.And lots of thanks.

Can you tell us the three letter engine code your car has? That will help to narrow down the technology of PD/non-PD engine, fuel filter system, etc. Some of the advice given so far may not apply to your car.

The code AWX

That helps to identify it as a PD engine, not an engine like the 03 Golf as mentioned above.

Do you hear the lift pump in the tank operate when you first turn the key? It is easier to hear if you roll down the window, or have the door open, and then turn the key to on. You should hear the pump operate for a second or two. The answer is probably yes.

The next question is whether you are getting sufficient fuel flow. Cold fuel doesn't flow as well as warm fuel. The fuel will be coldest in the morning. When, or how many miles ago, was the last fuel filter change? If over 15K miles, try replacing the fuel filter.

Your 02 model year was a split year for fuel filters. Does it have a fuel cooler on top of the filter and the filter screws onto it? Or is it the type where the fuel lines attach to the filter and a thermostatic control valve in the fuel return line?

hi pump operates,i put a non return fuel valve on to the fuel line.
filter changed 20k,i shall replace it,filter type fuel lines attach to the filter.
thanks.

filter changed see what it is like in the morning.

hi changed filter still the same prob,still need help boy's.